I have an LG GGW-H20L drive as well and it works fine on my Vista system with the OEM PowerDVD Ultra 7.3.3104a.
As soon as I tried to play my only “HD DVD” disc (King Kong) a critical update download prompt was triggered. I downloaded and installed the update which upgraded PowerDVD Ultra to version 7.3.3319.0. The HD DVD played fine before the update and after the update. I also downloaded the version OEM 3516 update but haven’t installed it yet.
I expect that Blu-Ray discs will be more problematic.